The invention concerns a vessel containing a plurality of separate beds of solid material, which beds can be discharged by gravity without mixing of material.
That vessel may be a reactor, a silo, etc.
The problem is found in particular in relation to reactors for the hydro-treatment of petroleum fractions, containing a plurality of separate, superposed catalytic beds, each bed containing a catalyst supported by a support plate. The support plates provide for separation as between the beds. The solid material is loaded into the vessel from an opening provided in the upper portion of the vessel.
The catalysts are not in the same state after operation, the problem at discharge being to avoid mixing thereof, which would inevitably occur if all the beds were discharged simultaneously at the bottom.
This problem also obviously arises when the beds are loaded with different catalysts.
In U.S. Pat. No. 4,642,223, at least one pipe is mounted on each support plate. The pipes of the highest support plate (corresponding to the bed which is closest to the upper opening of the vessel) are provided with removable baskets (which can be removed by a handle which can be pulled upwardly when the upper bed has been discharged) which are supported on the upper edge of the pipe and which provide for continuity of the support plate. The baskets then permit discharge of the upper bed by suction from the upper opening of the reactor. The pipes of the lower beds then do not have to comprise baskets so that discharge of the lower beds is effected by a flow under the effect of gravity from all the beds at the same time. The problem raised thus still remains entirely to be resolved.
U.S. Pat. No. 2,292,716 recommends the use of a rotary plate composed of two circular semi-sections which are fixed at their common diameter to a central beam about which they pivot. Each section of the plate bearing the catalytic bed is supported on at least one retractable bar member mounted in an opening in the wall of the reactor and retractable from the exterior of the reactor. Retraction of the bar member or members permits abrupt discharge of the catalyst. This in fact involves the material dropping on to the lower plate. In present installations in which the beds are frequently from 5 to 7 meters in height, it is clear that this drop can give rise to shocks, vibration and fractures of the lower plate and even the structure of the reactor. In addition, besides the problems in regard to sealing integrity, which are not overcome, it is clearly apparent that such plates are incapable of affording the necessary mechanical strength for supporting beds which generally weigh from 30 to 40 tonnes.